Ask HN: What are some great startups that started out "in stealth"?

Depending on what you mean by it, every one.

Do you mean a company like OnLive that was in stealth mode for many years?

Facebook might count, depending on what you mean by stealth.

Blekko - <a href="http://techcrunch.com/2009/11/04/stealth-search-engine-blekko-raises-another-2-5-million/" rel="nofollow">http://techcrunch.com/2009/11/04/stealth-search-engine-blekk...</a>